Cyclists are **required to wear a helmet** to protect themselves in case of accidents, as they are more vulnerable than other vehicles. However, there are exceptions to this rule. One of these exceptions is when cyclists are riding on **prolonged ascending slopes**. In these situations, the physical effort is greater, and cyclists are allowed not to wear a helmet to facilitate ventilation and comfort during the ascent.

It is important to note that this exception **does not apply** on descending slopes, as in these situations the speed can increase and the risk of accidents is higher, so wearing a helmet remains mandatory to ensure the cyclist's safety.